1. Field of the Invention
The present invention relates to a production method of a di(aminomethyl)-substituted aromatic compound by the hydrogenation of an aromatic dinitrile. The di(aminomethyl)-substituted aromatic compound is useful as the raw material for producing hardeners, synthetic resins, isocyanates, etc.
2. Description of the Prior Art
It has been proposed to hydrogenate an aromatic dinitrile in the presence of catalyst system containing various metals. For example, Japanese Patent Publication No. 51-24494 proposes a production method of 3-cyanobenzylamine or 4-cyanobenzylamine by the palladium-catalyzed hydrogenation of isophthalonitrile or terephthalonitrile in the presence of liquid ammonia and an inorganic alkali. Japanese Patent Application Laid-Open Nos. 9-40630 and 10-204048 propose production methods of aromatic cyanomethylamine (cyano(aminomethyl)-substituted aromatic compound) by hydrogenating one of the nitrile groups in an aromatic dinitrile in the presence of a nickel and/or cobalt-containing Raney catalyst. These patent documents only relate to the production of the aromatic cyanomethylamine, and describe nothing about the production of a diamine (di(aminomethyl)-substituted aromatic compound) corresponding thereto.
Japanese Patent Publication No. 10-502671 discloses a semi-hydrogenation of an aliphatic dinitrile into a corresponding aliphatic aminonitrile in the presence of a catalyst selected from the group consisting of Raney nickel catalysts containing a doping element such as zinc and elements in groups IVb, VIb, VIIb and VIII of the periodic table and Raney cobalt catalysts containing a doping element such as zinc and elements in groups IVb, VIb, VIIb and VIII of the periodic table. Japanese Patent Application Laid-Open No. 2001-524464 proposes a continuous partial hydrogenation of an aliphatic dinitrile into a corresponding aliphatic aminonitrile in a heterogeneous system in the presence of a hydrogenation catalyst. These patent documents only relate to the partial hydrogenation of the aliphatic dinitrile into the aliphatic aminonitrile, and describe nothing about the partial hydrogenation of the aromatic dinitrile into the aromatic cyanomethylamine and the subsequent hydrogenation of the aromatic cyanomethylamine into the corresponding diamine (di(aminomethyl)-substituted aromatic compound).
It has been further proposed to convert the aromatic dinitrile to the corresponding diamine (di(aminomethyl)-substituted aromatic compound) by a single step hydrogenation in the presence of a Ni- or Co-containing catalyst. For example, Japanese Patent Publication No. 38-8719 proposes the hydrogenation of phthalonitrile into the target xylylene diamine in alcohol containing a slight amount of water in the presence of a Raney nickel or Raney cobalt catalyst doped with caustic alkali. Japanese Patent Publication No. 48-22593 proposes the production of xylylene diamine from phthalonitrile in the presence of a supported nickel catalyst containing magnesium oxide as the co-catalyst. However, these methods fail to produce the target diamine in a sufficiently high yield because of the formation of by-products.